Cu-Cu Quasi-Direct Bonding with Atomically Thin-Au and Pt Intermediate Layer Using Atomic Layer Deposition

A low temperature Cu-Cu bonding technique using an atomically thin-Pt intermediate layer deposited by atomic layer deposition (ALD) was recently reported. In this study, we investigated the characteristic of the Cu-Cu quasi-direct bonding using different metal intermediate layers. A thin-Pt or Au intermediate layer were deposited on the Cu surface by ALD in angstrom level. Both the thin-Pt and the Au intermediate layer successfully improved the Cu-Cu bonding strength compared with that without thin-metal intermediate layer. Although Au is widely used as a thick-intermediate layer in conventional Cu-Cu bonding methods, the Cu-Cu quasi-direct bonding with thin-Pt layer obtained three times lager bonding strength (9.52 MPa) than that with thin-Au layer (3.20 MPa). These results are essential for developing low temperature Cu-Cu bonding for highly integrated 3D IC chips.